Somehow or other, this time of year I always come across the olde leaves-in-borders debate: To remove them now or wait until spring (or never, letting them decompose slowly)? This year it started innocently enough with a blog post for a garden center about what parts of my garden gets its leaves removed now, and why. I used the photo above to show two plants that could be ruined by being buried under wet leaves for too long, so I remove the leaves around them soon after they fall. These are Lambs’ Ears and a creeping Sedum, but I’d do the same for any dry-loving plant.
In the lower part of that photo are perennials that don’t mind being covered with leaves, so I’ll wait until all the leaves are down and maybe early spring before sending them off to the city’s compost-making operation.
Next, aesthetics. Above is a very prominent spot just outside my porch and living room window where the plants wouldn’t complain about leaves but I’d rather have the view below all winter. Also, I remove leaves from hard surfaces I walk on just for safety’s sake.
Then there’s the reason for early leaf removal that I was taught by a Carol Allen, trusted organic gardening guru to many in the DC area. She does it to remove diseased plant parts that may winter over, and spots for garden pests like mice and voles to winter over, too. She gets the leaf removal and mulching of her beds done by the end of December.
The Pro-Insect Position
But then someone sent me an article that entomologist Doug Tallamy recently wrote on the subject.
Unfortunately, the biggest threat to over-wintering insects doesn’t come from the weather. It comes from us, as we strive to “clean up” our flowerbeds, lawns, and meadows. A little knowledge about how insects spend the winter can help us avoid killing them unintentionally.”
Thick leaf litter is ideal for overwintering. This is just one more reason to retain, on your property, as many of your fallen leaves as you can.
The easiest way to preserve over-wintering insect populations is to relax our neatnik standards whenever possible. Plant the herbaceous perennials that spend the winter as dead stalks in less public areas of your properties. Come to realize that these stalks are not quite as dead as they seem, and are the normal condition of these plants in nature, a condition that many insects take advantage of during the fall and winter.
Well, I’m fine with leaving dead perennial stalks standing until spring; it’s the leaf litter that I worry about harboring pests that I’ll have to deal with next year – like aphids, black spot, voles and mice. I use no products in my garden – organic or otherwise – and garden clean-up helps avoid the need for any. Around trees and shrubs I think leaf litter’s probably fine, though.
Name those Critters!
But I’m on a quest for more specifics. Exactly what beneficial or pesky critters and diseases could be encouraged by a nice thick layer of leaf litter among perennials? Inquiring gardeners want to know! And if no definitive answers get posted in comments, what experts should I consult?
On the Toxicity of Introduced Plants
And this quote from Tallamy startled me:
Plants from Asia or Europe are typically toxic to our local insect herbivores, but these same insects are well equipped to avoid the toxic defenses employed by local native plants.
Does toxicity here mean that insects are harmed by these plants? Again, inquiring gardeners….
UPDATE: TALLAMY RESPONDS
In an email to me, which I also posted in the comment section: Very helpful~!